Microbiological Processes in Improving the Behavior of Soils for Civil Engineering Applications: A Critical Appraisal

Abstract

The application of biological processes to improve the behavior of soils remains a concern among the scientific, industrial, and public sectors. The amount of research in this field has increased in the last two decades. However, the complexities associated with this process for the types of soil and their heterogeneous behavior, longevity (i.e., durability), optimization of solutions and treatment methods, amount of calcite precipitation and uniformity in its distribution, upscaling in the field, and finding their effective measures require a comprehensive interdisciplinary research approach that combines geotechnical engineering, geochemistry, and microbiology. Therefore, this paper aims to encapsulate the research work from the last two decades by highlighting an overview of the mechanisms (i.e., biostimulation- and bioaugmentation-induced calcite precipitation) associated with the implications of biogeotechnology to improve the different soil types. The most commonly used biological processes [i.e., ureolysis or urea hydrolysis, denitrification, and sulfate (SO42–) or iron (Fe) reduction] will be compared for their suitability, limitations, and associated bacteria and strains that are used for the biotreatment of soils. In addition, various limiting factors that control the successful application of microbial-induced carbonate precipitation (MICP) to improve the properties of soils are highlighted. The fundamental differences between the biotreatment processes from the laboratory to field scale (e.g., injection method, surface percolation method, and premixing method) will be explained categorically. This paper will discuss the current status, challenges, and future opportunities in biogeotechnology. The application of biogeotechnology to improve the behavior of clayey soil requires more attention compared with sandy or silty soils. The major limitations, biological concerns, consequences, and their possible controlling measures will be discussed to understand the complexity when adopting biological processes in geotechnical projects and practices. Finally, the paper lists out the potential areas that should be focused on for the effective, economical, sustainable, and durable application of biogeotechnology under various construction conditions.